Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1255 insertions, 0 deletions

diff --git a/js/src/jit/x86/Trampoline-x86.cpp b/js/src/jit/x86/Trampoline-x86.cpp
new file mode 100644
index 0000000000..03c04eac0a
--- /dev/null
+++ b/js/src/jit/x86/Trampoline-x86.cpp
@@ -0,0 +1,1255 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/MathAlgorithms.h"
+
+#include "jit/Bailouts.h"
+#include "jit/BaselineFrame.h"
+#include "jit/BaselineJIT.h"
+#include "jit/CalleeToken.h"
+#include "jit/JitFrames.h"
+#include "jit/JitRuntime.h"
+#include "jit/JitSpewer.h"
+#ifdef JS_ION_PERF
+#  include "jit/PerfSpewer.h"
+#endif
+#include "jit/VMFunctions.h"
+#include "jit/x86/SharedICHelpers-x86.h"
+#include "vm/JitActivation.h"  // js::jit::JitActivation
+#include "vm/JSContext.h"
+#include "vm/Realm.h"
+#ifdef MOZ_VTUNE
+#  include "vtune/VTuneWrapper.h"
+#endif
+
+#include "jit/MacroAssembler-inl.h"
+#include "vm/JSScript-inl.h"
+
+using mozilla::IsPowerOfTwo;
+
+using namespace js;
+using namespace js::jit;
+
+// All registers to save and restore. This includes the stack pointer, since we
+// use the ability to reference register values on the stack by index.
+static const LiveRegisterSet AllRegs =
+    LiveRegisterSet(GeneralRegisterSet(Registers::AllMask),
+                    FloatRegisterSet(FloatRegisters::AllMask));
+
+enum EnterJitEbpArgumentOffset {
+  ARG_JITCODE = 2 * sizeof(void*),
+  ARG_ARGC = 3 * sizeof(void*),
+  ARG_ARGV = 4 * sizeof(void*),
+  ARG_STACKFRAME = 5 * sizeof(void*),
+  ARG_CALLEETOKEN = 6 * sizeof(void*),
+  ARG_SCOPECHAIN = 7 * sizeof(void*),
+  ARG_STACKVALUES = 8 * sizeof(void*),
+  ARG_RESULT = 9 * sizeof(void*)
+};
+
+// Generates a trampoline for calling Jit compiled code from a C++ function.
+// The trampoline use the EnterJitCode signature, with the standard cdecl
+// calling convention.
+void JitRuntime::generateEnterJIT(JSContext* cx, MacroAssembler& masm) {
+  enterJITOffset_ = startTrampolineCode(masm);
+
+  masm.assertStackAlignment(ABIStackAlignment,
+                            -int32_t(sizeof(uintptr_t)) /* return address */);
+
+  // Save old stack frame pointer, set new stack frame pointer.
+  masm.push(ebp);
+  masm.movl(esp, ebp);
+
+  // Save non-volatile registers. These must be saved by the trampoline,
+  // rather than the JIT'd code, because they are scanned by the conservative
+  // scanner.
+  masm.push(ebx);
+  masm.push(esi);
+  masm.push(edi);
+
+  // Keep track of the stack which has to be unwound after returning from the
+  // compiled function.
+  masm.movl(esp, esi);
+
+  // Load the number of values to be copied (argc) into eax
+  masm.loadPtr(Address(ebp, ARG_ARGC), eax);
+
+  // If we are constructing, that also needs to include newTarget
+  {
+    Label noNewTarget;
+    masm.loadPtr(Address(ebp, ARG_CALLEETOKEN), edx);
+    masm.branchTest32(Assembler::Zero, edx,
+                      Imm32(CalleeToken_FunctionConstructing), &noNewTarget);
+
+    masm.addl(Imm32(1), eax);
+
+    masm.bind(&noNewTarget);
+  }
+
+  // eax <- 8*numValues, eax is now the offset betwen argv and the last value.
+  masm.shll(Imm32(3), eax);
+
+  // Guarantee stack alignment of Jit frames.
+  //
+  // This code compensates for the offset created by the copy of the vector of
+  // arguments, such that the jit frame will be aligned once the return
+  // address is pushed on the stack.
+  //
+  // In the computation of the offset, we omit the size of the JitFrameLayout
+  // which is pushed on the stack, as the JitFrameLayout size is a multiple of
+  // the JitStackAlignment.
+  masm.movl(esp, ecx);
+  masm.subl(eax, ecx);
+  static_assert(
+      sizeof(JitFrameLayout) % JitStackAlignment == 0,
+      "No need to consider the JitFrameLayout for aligning the stack");
+
+  // ecx = ecx & 15, holds alignment.
+  masm.andl(Imm32(JitStackAlignment - 1), ecx);
+  masm.subl(ecx, esp);
+
+  /***************************************************************
+  Loop over argv vector, push arguments onto stack in reverse order
+  ***************************************************************/
+
+  // ebx = argv   --argv pointer is in ebp + 16
+  masm.loadPtr(Address(ebp, ARG_ARGV), ebx);
+
+  // eax = argv[8(argc)]  --eax now points one value past the last argument
+  masm.addl(ebx, eax);
+
+  // while (eax > ebx)  --while still looping through arguments
+  {
+    Label header, footer;
+    masm.bind(&header);
+
+    masm.cmp32(eax, ebx);
+    masm.j(Assembler::BelowOrEqual, &footer);
+
+    // eax -= 8  --move to previous argument
+    masm.subl(Imm32(8), eax);
+
+    // Push what eax points to on stack, a Value is 2 words
+    masm.push(Operand(eax, 4));
+    masm.push(Operand(eax, 0));
+
+    masm.jmp(&header);
+    masm.bind(&footer);
+  }
+
+  // Push the number of actual arguments.  |result| is used to store the
+  // actual number of arguments without adding an extra argument to the enter
+  // JIT.
+  masm.mov(Operand(ebp, ARG_RESULT), eax);
+  masm.unboxInt32(Address(eax, 0x0), eax);
+  masm.push(eax);
+
+  // Push the callee token.
+  masm.push(Operand(ebp, ARG_CALLEETOKEN));
+
+  // Load the InterpreterFrame address into the OsrFrameReg.
+  // This address is also used for setting the constructing bit on all paths.
+  masm.loadPtr(Address(ebp, ARG_STACKFRAME), OsrFrameReg);
+
+  /*****************************************************************
+  Push the number of bytes we've pushed so far on the stack and call
+  *****************************************************************/
+  // Create a frame descriptor.
+  masm.subl(esp, esi);
+  masm.makeFrameDescriptor(esi, FrameType::CppToJSJit, JitFrameLayout::Size());
+  masm.push(esi);
+
+  CodeLabel returnLabel;
+  CodeLabel oomReturnLabel;
+  {
+    // Handle Interpreter -> Baseline OSR.
+    AllocatableGeneralRegisterSet regs(GeneralRegisterSet::All());
+    regs.take(JSReturnOperand);
+    regs.takeUnchecked(OsrFrameReg);
+    regs.take(ebp);
+    regs.take(ReturnReg);
+
+    Register scratch = regs.takeAny();
+
+    Label notOsr;
+    masm.branchTestPtr(Assembler::Zero, OsrFrameReg, OsrFrameReg, &notOsr);
+
+    Register numStackValues = regs.takeAny();
+    masm.loadPtr(Address(ebp, ARG_STACKVALUES), numStackValues);
+
+    Register jitcode = regs.takeAny();
+    masm.loadPtr(Address(ebp, ARG_JITCODE), jitcode);
+
+    // Push return address.
+    masm.mov(&returnLabel, scratch);
+    masm.push(scratch);
+
+    // Push previous frame pointer.
+    masm.push(ebp);
+
+    // Reserve frame.
+    Register framePtr = ebp;
+    masm.subPtr(Imm32(BaselineFrame::Size()), esp);
+
+    masm.touchFrameValues(numStackValues, scratch, framePtr);
+    masm.mov(esp, framePtr);
+
+    // Reserve space for locals and stack values.
+    masm.mov(numStackValues, scratch);
+    masm.shll(Imm32(3), scratch);
+    masm.subPtr(scratch, esp);
+
+    // Enter exit frame.
+    masm.addPtr(
+        Imm32(BaselineFrame::Size() + BaselineFrame::FramePointerOffset),
+        scratch);
+    masm.makeFrameDescriptor(scratch, FrameType::BaselineJS,
+                             ExitFrameLayout::Size());
+    masm.push(scratch);  // Fake return address.
+    masm.push(Imm32(0));
+    // No GC things to mark on the stack, push a bare token.
+    masm.loadJSContext(scratch);
+    masm.enterFakeExitFrame(scratch, scratch, ExitFrameType::Bare);
+
+    masm.push(framePtr);
+    masm.push(jitcode);
+
+    using Fn = bool (*)(BaselineFrame * frame, InterpreterFrame * interpFrame,
+                        uint32_t numStackValues);
+    masm.setupUnalignedABICall(scratch);
+    masm.passABIArg(framePtr);     // BaselineFrame
+    masm.passABIArg(OsrFrameReg);  // InterpreterFrame
+    masm.passABIArg(numStackValues);
+    masm.callWithABI<Fn, jit::InitBaselineFrameForOsr>(
+        MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+    masm.pop(jitcode);
+    masm.pop(framePtr);
+
+    MOZ_ASSERT(jitcode != ReturnReg);
+
+    Label error;
+    masm.addPtr(Imm32(ExitFrameLayout::SizeWithFooter()), esp);
+    masm.addPtr(Imm32(BaselineFrame::Size()), framePtr);
+    masm.branchIfFalseBool(ReturnReg, &error);
+
+    // If OSR-ing, then emit instrumentation for setting lastProfilerFrame
+    // if profiler instrumentation is enabled.
+    {
+      Label skipProfilingInstrumentation;
+      Register realFramePtr = numStackValues;
+      AbsoluteAddress addressOfEnabled(
+          cx->runtime()->geckoProfiler().addressOfEnabled());
+      masm.branch32(Assembler::Equal, addressOfEnabled, Imm32(0),
+                    &skipProfilingInstrumentation);
+      masm.lea(Operand(framePtr, sizeof(void*)), realFramePtr);
+      masm.profilerEnterFrame(realFramePtr, scratch);
+      masm.bind(&skipProfilingInstrumentation);
+    }
+
+    masm.jump(jitcode);
+
+    // OOM: load error value, discard return address and previous frame
+    // pointer and return.
+    masm.bind(&error);
+    masm.mov(framePtr, esp);
+    masm.addPtr(Imm32(2 * sizeof(uintptr_t)), esp);
+    masm.moveValue(MagicValue(JS_ION_ERROR), JSReturnOperand);
+    masm.mov(&oomReturnLabel, scratch);
+    masm.jump(scratch);
+
+    masm.bind(&notOsr);
+    masm.loadPtr(Address(ebp, ARG_SCOPECHAIN), R1.scratchReg());
+  }
+
+  // The call will push the return address on the stack, thus we check that
+  // the stack would be aligned once the call is complete.
+  masm.assertStackAlignment(JitStackAlignment, sizeof(uintptr_t));
+
+  /***************************************************************
+      Call passed-in code, get return value and fill in the
+      passed in return value pointer
+  ***************************************************************/
+  masm.call(Address(ebp, ARG_JITCODE));
+
+  {
+    // Interpreter -> Baseline OSR will return here.
+    masm.bind(&returnLabel);
+    masm.addCodeLabel(returnLabel);
+    masm.bind(&oomReturnLabel);
+    masm.addCodeLabel(oomReturnLabel);
+  }
+
+  // Pop arguments off the stack.
+  // eax <- 8*argc (size of all arguments we pushed on the stack)
+  masm.pop(eax);
+  masm.shrl(Imm32(FRAMESIZE_SHIFT), eax);  // Unmark EntryFrame.
+  masm.addl(eax, esp);
+
+  // |ebp| could have been clobbered by the inner function.
+  // Grab the address for the Value result from the argument stack.
+  //  +20 ... arguments ...
+  //  +16 <return>
+  //  +12 ebp <- original %ebp pointing here.
+  //  +8  ebx
+  //  +4  esi
+  //  +0  edi
+  masm.loadPtr(Address(esp, ARG_RESULT + 3 * sizeof(void*)), eax);
+  masm.storeValue(JSReturnOperand, Operand(eax, 0));
+
+  /**************************************************************
+      Return stack and registers to correct state
+  **************************************************************/
+
+  // Restore non-volatile registers
+  masm.pop(edi);
+  masm.pop(esi);
+  masm.pop(ebx);
+
+  // Restore old stack frame pointer
+  masm.pop(ebp);
+  masm.ret();
+}
+
+// Push AllRegs in a way that is compatible with RegisterDump, regardless of
+// what PushRegsInMask might do to reduce the set size.
+static void DumpAllRegs(MacroAssembler& masm) {
+#ifdef ENABLE_WASM_SIMD
+  masm.PushRegsInMask(AllRegs);
+#else
+  // When SIMD isn't supported, PushRegsInMask reduces the set of float
+  // registers to be double-sized, while the RegisterDump expects each of
+  // the float registers to have the maximal possible size
+  // (Simd128DataSize). To work around this, we just spill the double
+  // registers by hand here, using the register dump offset directly.
+  for (GeneralRegisterBackwardIterator iter(AllRegs.gprs()); iter.more();
+       ++iter) {
+    masm.Push(*iter);
+  }
+
+  masm.reserveStack(sizeof(RegisterDump::FPUArray));
+  for (FloatRegisterBackwardIterator iter(AllRegs.fpus()); iter.more();
+       ++iter) {
+    FloatRegister reg = *iter;
+    Address spillAddress(StackPointer, reg.getRegisterDumpOffsetInBytes());
+    masm.storeDouble(reg, spillAddress);
+  }
+#endif
+}
+
+void JitRuntime::generateInvalidator(MacroAssembler& masm, Label* bailoutTail) {
+  invalidatorOffset_ = startTrampolineCode(masm);
+
+  // We do the minimum amount of work in assembly and shunt the rest
+  // off to InvalidationBailout. Assembly does:
+  //
+  // - Push the machine state onto the stack.
+  // - Call the InvalidationBailout routine with the stack pointer.
+  // - Now that the frame has been bailed out, convert the invalidated
+  //   frame into an exit frame.
+  // - Do the normal check-return-code-and-thunk-to-the-interpreter dance.
+
+  // Push registers such that we can access them from [base + code].
+  DumpAllRegs(masm);
+
+  masm.movl(esp, eax);  // Argument to jit::InvalidationBailout.
+
+  // Make space for InvalidationBailout's frameSize outparam.
+  masm.reserveStack(sizeof(size_t));
+  masm.movl(esp, ebx);
+
+  // Make space for InvalidationBailout's bailoutInfo outparam.
+  masm.reserveStack(sizeof(void*));
+  masm.movl(esp, ecx);
+
+  using Fn = bool (*)(InvalidationBailoutStack * sp, size_t * frameSizeOut,
+                      BaselineBailoutInfo * *info);
+  masm.setupUnalignedABICall(edx);
+  masm.passABIArg(eax);
+  masm.passABIArg(ebx);
+  masm.passABIArg(ecx);
+  masm.callWithABI<Fn, InvalidationBailout>(
+      MoveOp::GENERAL, CheckUnsafeCallWithABI::DontCheckOther);
+
+  masm.pop(ecx);  // Get bailoutInfo outparam.
+  masm.pop(ebx);  // Get the frameSize outparam.
+
+  // Pop the machine state and the dead frame.
+  masm.lea(Operand(esp, ebx, TimesOne, sizeof(InvalidationBailoutStack)), esp);
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in ecx.
+  masm.jmp(bailoutTail);
+}
+
+void JitRuntime::generateArgumentsRectifier(MacroAssembler& masm,
+                                            ArgumentsRectifierKind kind) {
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      argumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      trialInliningArgumentsRectifierOffset_ = startTrampolineCode(masm);
+      break;
+  }
+
+  // Caller:
+  // [arg2] [arg1] [this] [ [argc] [callee] [descr] [raddr] ] <- esp
+
+  // Load argc.
+  masm.loadPtr(Address(esp, RectifierFrameLayout::offsetOfNumActualArgs()),
+               esi);
+
+  // Load the number of |undefined|s to push into %ecx.
+  masm.loadPtr(Address(esp, RectifierFrameLayout::offsetOfCalleeToken()), eax);
+  masm.mov(eax, ecx);
+  masm.andl(Imm32(CalleeTokenMask), ecx);
+  masm.movzwl(Operand(ecx, JSFunction::offsetOfNargs()), ecx);
+
+  // The frame pointer and its padding are pushed on the stack.
+  // Including |this|, there are (|nformals| + 1) arguments to push to the
+  // stack.  Then we push a JitFrameLayout.  We compute the padding expressed
+  // in the number of extra |undefined| values to push on the stack.
+  static_assert(
+      sizeof(JitFrameLayout) % JitStackAlignment == 0,
+      "No need to consider the JitFrameLayout for aligning the stack");
+  static_assert((sizeof(Value) + 2 * sizeof(void*)) % JitStackAlignment == 0,
+                "No need to consider |this| and the frame pointer and its "
+                "padding for aligning the stack");
+  static_assert(
+      JitStackAlignment % sizeof(Value) == 0,
+      "Ensure that we can pad the stack by pushing extra UndefinedValue");
+  static_assert(IsPowerOfTwo(JitStackValueAlignment),
+                "must have power of two for masm.andl to do its job");
+
+  masm.addl(Imm32(JitStackValueAlignment - 1 /* for padding */), ecx);
+
+  // Account for newTarget, if necessary.
+  static_assert(
+      CalleeToken_FunctionConstructing == 1,
+      "Ensure that we can use the constructing bit to count an extra push");
+  masm.mov(eax, edx);
+  masm.andl(Imm32(CalleeToken_FunctionConstructing), edx);
+  masm.addl(edx, ecx);
+
+  masm.andl(Imm32(~(JitStackValueAlignment - 1)), ecx);
+  masm.subl(esi, ecx);
+
+  // Copy the number of actual arguments into edx.
+  masm.mov(esi, edx);
+
+  masm.moveValue(UndefinedValue(), ValueOperand(ebx, edi));
+
+  // NOTE: The fact that x86 ArgumentsRectifier saves the FramePointer
+  // is relied upon by the baseline bailout code.  If this changes,
+  // fix that code!  See the |#if defined(JS_CODEGEN_X86) portions of
+  // BaselineStackBuilder::calculatePrevFramePtr and
+  // BaselineStackBuilder::buildRectifierFrame (in BaselineBailouts.cpp).
+  masm.push(FramePointer);
+  masm.movl(esp, FramePointer);  // Save %esp.
+  masm.push(FramePointer /* padding */);
+
+  // Caller:
+  // [arg2] [arg1] [this] [ [argc] [callee] [descr] [raddr] ]
+  // '-- #esi ---'
+  //
+  // Rectifier frame:
+  // [ebp'] <- ebp [padding] <- esp [undef] [undef] [arg2] [arg1] [this]
+  //                                '--- #ecx ----' '-- #esi ---'
+  //
+  // [ [argc] [callee] [descr] [raddr] ]
+
+  // Push undefined.
+  {
+    Label undefLoopTop;
+    masm.bind(&undefLoopTop);
+
+    masm.push(ebx);  // type(undefined);
+    masm.push(edi);  // payload(undefined);
+    masm.subl(Imm32(1), ecx);
+    masm.j(Assembler::NonZero, &undefLoopTop);
+  }
+
+  // Get the topmost argument. We did a push of %ebp earlier, so be sure to
+  // account for this in the offset
+  BaseIndex b(FramePointer, esi, TimesEight,
+              sizeof(RectifierFrameLayout) + sizeof(void*));
+  masm.lea(Operand(b), ecx);
+
+  // Push arguments, |nargs| + 1 times (to include |this|).
+  masm.addl(Imm32(1), esi);
+  {
+    Label copyLoopTop;
+
+    masm.bind(&copyLoopTop);
+    masm.push(Operand(ecx, sizeof(Value) / 2));
+    masm.push(Operand(ecx, 0x0));
+    masm.subl(Imm32(sizeof(Value)), ecx);
+    masm.subl(Imm32(1), esi);
+    masm.j(Assembler::NonZero, &copyLoopTop);
+  }
+
+  {
+    Label notConstructing;
+
+    masm.mov(eax, ebx);
+    masm.branchTest32(Assembler::Zero, ebx,
+                      Imm32(CalleeToken_FunctionConstructing),
+                      &notConstructing);
+
+    BaseValueIndex src(
+        FramePointer, edx,
+        sizeof(RectifierFrameLayout) + sizeof(Value) + sizeof(void*));
+
+    masm.andl(Imm32(CalleeTokenMask), ebx);
+    masm.movzwl(Operand(ebx, JSFunction::offsetOfNargs()), ebx);
+
+    BaseValueIndex dst(esp, ebx, sizeof(Value));
+
+    ValueOperand newTarget(ecx, edi);
+
+    masm.loadValue(src, newTarget);
+    masm.storeValue(newTarget, dst);
+
+    masm.bind(&notConstructing);
+  }
+
+  // Construct descriptor, accounting for pushed frame pointer above
+  masm.lea(Operand(FramePointer, sizeof(void*)), ebx);
+  masm.subl(esp, ebx);
+  masm.makeFrameDescriptor(ebx, FrameType::Rectifier, JitFrameLayout::Size());
+
+  // Construct JitFrameLayout.
+  masm.push(edx);  // number of actual arguments
+  masm.push(eax);  // callee token
+  masm.push(ebx);  // descriptor
+
+  // Call the target function.
+  masm.andl(Imm32(CalleeTokenMask), eax);
+  switch (kind) {
+    case ArgumentsRectifierKind::Normal:
+      masm.loadJitCodeRaw(eax, eax);
+      argumentsRectifierReturnOffset_ = masm.callJitNoProfiler(eax);
+      break;
+    case ArgumentsRectifierKind::TrialInlining:
+      Label noBaselineScript, done;
+      masm.loadBaselineJitCodeRaw(eax, ebx, &noBaselineScript);
+      masm.callJitNoProfiler(ebx);
+      masm.jump(&done);
+
+      // See BaselineCacheIRCompiler::emitCallInlinedFunction.
+      masm.bind(&noBaselineScript);
+      masm.loadJitCodeRaw(eax, eax);
+      masm.callJitNoProfiler(eax);
+      masm.bind(&done);
+      break;
+  }
+
+  // Remove the rectifier frame.
+  masm.pop(ebx);                           // ebx <- descriptor with FrameType.
+  masm.shrl(Imm32(FRAMESIZE_SHIFT), ebx);  // ebx <- descriptor.
+  masm.pop(edi);                           // Discard calleeToken.
+  masm.pop(edi);  // Discard number of actual arguments.
+
+  // Discard pushed arguments, but not the pushed frame pointer.
+  BaseIndex unwind(esp, ebx, TimesOne, -int32_t(sizeof(void*)));
+  masm.lea(Operand(unwind), esp);
+
+  masm.pop(FramePointer);
+  masm.ret();
+}
+
+static void PushBailoutFrame(MacroAssembler& masm, uint32_t frameClass,
+                             Register spArg) {
+  // Push registers such that we can access them from [base + code].
+  DumpAllRegs(masm);
+
+  // Push the bailout table number.
+  masm.push(Imm32(frameClass));
+
+  // The current stack pointer is the first argument to jit::Bailout.
+  masm.movl(esp, spArg);
+}
+
+static void GenerateBailoutThunk(MacroAssembler& masm, uint32_t frameClass,
+                                 Label* bailoutTail) {
+  PushBailoutFrame(masm, frameClass, eax);
+
+  // Make space for Bailout's baioutInfo outparam.
+  masm.reserveStack(sizeof(void*));
+  masm.movl(esp, ebx);
+
+  // Call the bailout function. This will correct the size of the bailout.
+  using Fn = bool (*)(BailoutStack * sp, BaselineBailoutInfo * *info);
+  masm.setupUnalignedABICall(ecx);
+  masm.passABIArg(eax);
+  masm.passABIArg(ebx);
+  masm.callWithABI<Fn, Bailout>(MoveOp::GENERAL,
+                                CheckUnsafeCallWithABI::DontCheckOther);
+
+  masm.pop(ecx);  // Get bailoutInfo outparam.
+
+  // Common size of stuff we've pushed.
+  static const uint32_t BailoutDataSize = 0 + sizeof(void*)  // frameClass
+                                          + sizeof(RegisterDump);
+
+  // Remove both the bailout frame and the topmost Ion frame's stack.
+  if (frameClass == NO_FRAME_SIZE_CLASS_ID) {
+    // We want the frameSize. Stack is:
+    //    ... frame ...
+    //    snapshotOffset
+    //    frameSize
+    //    ... bailoutFrame ...
+    masm.addl(Imm32(BailoutDataSize), esp);
+    masm.pop(ebx);
+    masm.addl(Imm32(sizeof(uint32_t)), esp);
+    masm.addl(ebx, esp);
+  } else {
+    // Stack is:
+    //    ... frame ...
+    //    bailoutId
+    //    ... bailoutFrame ...
+    uint32_t frameSize = FrameSizeClass::FromClass(frameClass).frameSize();
+    masm.addl(Imm32(BailoutDataSize + sizeof(void*) + frameSize), esp);
+  }
+
+  // Jump to shared bailout tail. The BailoutInfo pointer has to be in ecx.
+  masm.jmp(bailoutTail);
+}
+
+JitRuntime::BailoutTable JitRuntime::generateBailoutTable(MacroAssembler& masm,
+                                                          Label* bailoutTail,
+                                                          uint32_t frameClass) {
+  uint32_t offset = startTrampolineCode(masm);
+
+  Label bailout;
+  for (size_t i = 0; i < BAILOUT_TABLE_SIZE; i++) {
+    masm.call(&bailout);
+  }
+  masm.bind(&bailout);
+
+  GenerateBailoutThunk(masm, frameClass, bailoutTail);
+
+  return BailoutTable(offset, masm.currentOffset() - offset);
+}
+
+void JitRuntime::generateBailoutHandler(MacroAssembler& masm,
+                                        Label* bailoutTail) {
+  bailoutHandlerOffset_ = startTrampolineCode(masm);
+
+  GenerateBailoutThunk(masm, NO_FRAME_SIZE_CLASS_ID, bailoutTail);
+}
+
+bool JitRuntime::generateVMWrapper(JSContext* cx, MacroAssembler& masm,
+                                   const VMFunctionData& f, DynFn nativeFun,
+                                   uint32_t* wrapperOffset) {
+  *wrapperOffset = startTrampolineCode(masm);
+
+  // Avoid conflicts with argument registers while discarding the result after
+  // the function call.
+  AllocatableGeneralRegisterSet regs(Register::Codes::WrapperMask);
+
+  static_assert(
+      (Register::Codes::VolatileMask & ~Register::Codes::WrapperMask) == 0,
+      "Wrapper register set must be a superset of Volatile register set.");
+
+  // The context is the first argument.
+  Register cxreg = regs.takeAny();
+
+  // Stack is:
+  //    ... frame ...
+  //  +8  [args]
+  //  +4  descriptor
+  //  +0  returnAddress
+  //
+  // We're aligned to an exit frame, so link it up.
+  masm.loadJSContext(cxreg);
+  masm.enterExitFrame(cxreg, regs.getAny(), &f);
+
+  // Save the current stack pointer as the base for copying arguments.
+  Register argsBase = InvalidReg;
+  if (f.explicitArgs) {
+    argsBase = regs.takeAny();
+    masm.lea(Operand(esp, ExitFrameLayout::SizeWithFooter()), argsBase);
+  }
+
+  // Reserve space for the outparameter.
+  Register outReg = InvalidReg;
+  switch (f.outParam) {
+    case Type_Value:
+      outReg = regs.takeAny();
+      masm.Push(UndefinedValue());
+      masm.movl(esp, outReg);
+      break;
+
+    case Type_Handle:
+      outReg = regs.takeAny();
+      masm.PushEmptyRooted(f.outParamRootType);
+      masm.movl(esp, outReg);
+      break;
+
+    case Type_Int32:
+    case Type_Pointer:
+    case Type_Bool:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(int32_t));
+      masm.movl(esp, outReg);
+      break;
+
+    case Type_Double:
+      outReg = regs.takeAny();
+      masm.reserveStack(sizeof(double));
+      masm.movl(esp, outReg);
+      break;
+
+    default:
+      MOZ_ASSERT(f.outParam == Type_Void);
+      break;
+  }
+
+  if (!generateTLEnterVM(masm, f)) {
+    return false;
+  }
+
+  masm.setupUnalignedABICall(regs.getAny());
+  masm.passABIArg(cxreg);
+
+  size_t argDisp = 0;
+
+  // Copy arguments.
+  for (uint32_t explicitArg = 0; explicitArg < f.explicitArgs; explicitArg++) {
+    switch (f.argProperties(explicitArg)) {
+      case VMFunctionData::WordByValue:
+        masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+      case VMFunctionData::DoubleByValue:
+        // We don't pass doubles in float registers on x86, so no need
+        // to check for argPassedInFloatReg.
+        masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        masm.passABIArg(MoveOperand(argsBase, argDisp), MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+      case VMFunctionData::WordByRef:
+        masm.passABIArg(
+            MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+            MoveOp::GENERAL);
+        argDisp += sizeof(void*);
+        break;
+      case VMFunctionData::DoubleByRef:
+        masm.passABIArg(
+            MoveOperand(argsBase, argDisp, MoveOperand::EFFECTIVE_ADDRESS),
+            MoveOp::GENERAL);
+        argDisp += 2 * sizeof(void*);
+        break;
+    }
+  }
+
+  // Copy the implicit outparam, if any.
+  if (outReg != InvalidReg) {
+    masm.passABIArg(outReg);
+  }
+
+  masm.callWithABI(nativeFun, MoveOp::GENERAL,
+                   CheckUnsafeCallWithABI::DontCheckHasExitFrame);
+
+  if (!generateTLExitVM(masm, f)) {
+    return false;
+  }
+
+  // Test for failure.
+  switch (f.failType()) {
+    case Type_Object:
+      masm.branchTestPtr(Assembler::Zero, eax, eax, masm.failureLabel());
+      break;
+    case Type_Bool:
+      masm.testb(eax, eax);
+      masm.j(Assembler::Zero, masm.failureLabel());
+      break;
+    case Type_Void:
+      break;
+    default:
+      MOZ_CRASH("unknown failure kind");
+  }
+
+  // Load the outparam and free any allocated stack.
+  switch (f.outParam) {
+    case Type_Handle:
+      masm.popRooted(f.outParamRootType, ReturnReg, JSReturnOperand);
+      break;
+
+    case Type_Value:
+      masm.Pop(JSReturnOperand);
+      break;
+
+    case Type_Int32:
+    case Type_Pointer:
+      masm.Pop(ReturnReg);
+      break;
+
+    case Type_Bool:
+      masm.Pop(ReturnReg);
+      masm.movzbl(ReturnReg, ReturnReg);
+      break;
+
+    case Type_Double:
+      if (JitOptions.supportsFloatingPoint) {
+        masm.Pop(ReturnDoubleReg);
+      } else {
+        masm.assumeUnreachable(
+            "Unable to pop to float reg, with no FP support.");
+      }
+      break;
+
+    default:
+      MOZ_ASSERT(f.outParam == Type_Void);
+      break;
+  }
+
+  // Until C++ code is instrumented against Spectre, prevent speculative
+  // execution from returning any private data.
+  if (f.returnsData() && JitOptions.spectreJitToCxxCalls) {
+    masm.speculationBarrier();
+  }
+
+  masm.leaveExitFrame();
+  masm.retn(Imm32(sizeof(ExitFrameLayout) +
+                  f.explicitStackSlots() * sizeof(void*) +
+                  f.extraValuesToPop * sizeof(Value)));
+
+  return true;
+}
+
+uint32_t JitRuntime::generatePreBarrier(JSContext* cx, MacroAssembler& masm,
+                                        MIRType type) {
+  uint32_t offset = startTrampolineCode(masm);
+
+  static_assert(PreBarrierReg == edx);
+  Register temp1 = eax;
+  Register temp2 = ebx;
+  Register temp3 = ecx;
+  masm.push(temp1);
+  masm.push(temp2);
+  masm.push(temp3);
+
+  Label noBarrier;
+  masm.emitPreBarrierFastPath(cx->runtime(), type, temp1, temp2, temp3,
+                              &noBarrier);
+
+  // Call into C++ to mark this GC thing.
+  masm.pop(temp3);
+  masm.pop(temp2);
+  masm.pop(temp1);
+
+  LiveRegisterSet save;
+  if (JitOptions.supportsFloatingPoint) {
+    save.set() = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                             FloatRegisterSet(FloatRegisters::VolatileMask));
+  } else {
+    save.set() = RegisterSet(GeneralRegisterSet(Registers::VolatileMask),
+                             FloatRegisterSet());
+  }
+  masm.PushRegsInMask(save);
+
+  masm.movl(ImmPtr(cx->runtime()), ecx);
+
+  masm.setupUnalignedABICall(eax);
+  masm.passABIArg(ecx);
+  masm.passABIArg(edx);
+  masm.callWithABI(JitMarkFunction(type));
+
+  masm.PopRegsInMask(save);
+  masm.ret();
+
+  masm.bind(&noBarrier);
+  masm.pop(temp3);
+  masm.pop(temp2);
+  masm.pop(temp1);
+  masm.ret();
+
+  return offset;
+}
+
+void JitRuntime::generateExceptionTailStub(MacroAssembler& masm,
+                                           Label* profilerExitTail) {
+  exceptionTailOffset_ = startTrampolineCode(masm);
+
+  masm.bind(masm.failureLabel());
+  masm.handleFailureWithHandlerTail(profilerExitTail);
+}
+
+void JitRuntime::generateBailoutTailStub(MacroAssembler& masm,
+                                         Label* bailoutTail) {
+  bailoutTailOffset_ = startTrampolineCode(masm);
+  masm.bind(bailoutTail);
+
+  masm.generateBailoutTail(edx, ecx);
+}
+
+void JitRuntime::generateProfilerExitFrameTailStub(MacroAssembler& masm,
+                                                   Label* profilerExitTail) {
+  profilerExitFrameTailOffset_ = startTrampolineCode(masm);
+  masm.bind(profilerExitTail);
+
+  Register scratch1 = eax;
+  Register scratch2 = ebx;
+  Register scratch3 = esi;
+  Register scratch4 = edi;
+
+  //
+  // The code generated below expects that the current stack pointer points
+  // to an Ion or Baseline frame, at the state it would be immediately
+  // before a ret().  Thus, after this stub's business is done, it executes
+  // a ret() and returns directly to the caller script, on behalf of the
+  // callee script that jumped to this code.
+  //
+  // Thus the expected stack is:
+  //
+  //                                   StackPointer ----+
+  //                                                    v
+  // ..., ActualArgc, CalleeToken, Descriptor, ReturnAddr
+  // MEM-HI                                       MEM-LOW
+  //
+  //
+  // The generated jitcode is responsible for overwriting the
+  // jitActivation->lastProfilingFrame field with a pointer to the previous
+  // Ion or Baseline jit-frame that was pushed before this one. It is also
+  // responsible for overwriting jitActivation->lastProfilingCallSite with
+  // the return address into that frame.  The frame could either be an
+  // immediate "caller" frame, or it could be a frame in a previous
+  // JitActivation (if the current frame was entered from C++, and the C++
+  // was entered by some caller jit-frame further down the stack).
+  //
+  // So this jitcode is responsible for "walking up" the jit stack, finding
+  // the previous Ion or Baseline JS frame, and storing its address and the
+  // return address into the appropriate fields on the current jitActivation.
+  //
+  // There are a fixed number of different path types that can lead to the
+  // current frame, which is either a baseline or ion frame:
+  //
+  // <Baseline-Or-Ion>
+  // ^
+  // |
+  // ^--- Ion
+  // |
+  // ^--- Baseline Stub <---- Baseline
+  // |
+  // ^--- Argument Rectifier
+  // |    ^
+  // |    |
+  // |    ^--- Ion
+  // |    |
+  // |    ^--- Baseline Stub <---- Baseline
+  // |
+  // ^--- Entry Frame (From C++)
+  //
+  Register actReg = scratch4;
+  masm.loadJSContext(actReg);
+  masm.loadPtr(Address(actReg, offsetof(JSContext, profilingActivation_)),
+               actReg);
+
+  Address lastProfilingFrame(actReg,
+                             JitActivation::offsetOfLastProfilingFrame());
+  Address lastProfilingCallSite(actReg,
+                                JitActivation::offsetOfLastProfilingCallSite());
+
+#ifdef DEBUG
+  // Ensure that frame we are exiting is current lastProfilingFrame
+  {
+    masm.loadPtr(lastProfilingFrame, scratch1);
+    Label checkOk;
+    masm.branchPtr(Assembler::Equal, scratch1, ImmWord(0), &checkOk);
+    masm.branchPtr(Assembler::Equal, StackPointer, scratch1, &checkOk);
+    masm.assumeUnreachable(
+        "Mismatch between stored lastProfilingFrame and current stack "
+        "pointer.");
+    masm.bind(&checkOk);
+  }
+#endif
+
+  // Load the frame descriptor into |scratch1|, figure out what to do
+  // depending on its type.
+  masm.loadPtr(Address(StackPointer, JitFrameLayout::offsetOfDescriptor()),
+               scratch1);
+
+  // Going into the conditionals, we will have:
+  //      FrameDescriptor.size in scratch1
+  //      FrameDescriptor.type in scratch2
+  masm.movePtr(scratch1, scratch2);
+  masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch1);
+  masm.and32(Imm32((1 << FRAMETYPE_BITS) - 1), scratch2);
+
+  // Handling of each case is dependent on FrameDescriptor.type
+  Label handle_IonJS;
+  Label handle_BaselineStub;
+  Label handle_Rectifier;
+  Label handle_IonICCall;
+  Label handle_Entry;
+  Label end;
+
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::IonJS),
+                &handle_IonJS);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::BaselineJS),
+                &handle_IonJS);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::BaselineStub),
+                &handle_BaselineStub);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::Rectifier),
+                &handle_Rectifier);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::IonICCall),
+                &handle_IonICCall);
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::CppToJSJit),
+                &handle_Entry);
+
+  // The WasmToJSJit is just another kind of entry.
+  masm.branch32(Assembler::Equal, scratch2, Imm32(FrameType::WasmToJSJit),
+                &handle_Entry);
+
+  masm.assumeUnreachable(
+      "Invalid caller frame type when exiting from Ion frame.");
+
+  //
+  // FrameType::IonJS
+  //
+  // Stack layout:
+  //                  ...
+  //                  Ion-Descriptor
+  //     Prev-FP ---> Ion-ReturnAddr
+  //                  ... previous frame data ... |- Descriptor.Size
+  //                  ... arguments ...           |
+  //                  ActualArgc          |
+  //                  CalleeToken         |- JitFrameLayout::Size()
+  //                  Descriptor          |
+  //        FP -----> ReturnAddr          |
+  //
+  masm.bind(&handle_IonJS);
+  {
+    // |scratch1| contains Descriptor.size
+
+    // returning directly to an IonJS frame.  Store return addr to frame
+    // in lastProfilingCallSite.
+    masm.loadPtr(Address(StackPointer, JitFrameLayout::offsetOfReturnAddress()),
+                 scratch2);
+    masm.storePtr(scratch2, lastProfilingCallSite);
+
+    // Store return frame in lastProfilingFrame.
+    // scratch2 := StackPointer + Descriptor.size*1 + JitFrameLayout::Size();
+    masm.lea(Operand(StackPointer, scratch1, TimesOne, JitFrameLayout::Size()),
+             scratch2);
+    masm.storePtr(scratch2, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::BaselineStub
+  //
+  // Look past the stub and store the frame pointer to
+  // the baselineJS frame prior to it.
+  //
+  // Stack layout:
+  //              ...
+  //              BL-Descriptor
+  // Prev-FP ---> BL-ReturnAddr
+  //      +-----> BL-PrevFramePointer
+  //      |       ... BL-FrameData ...
+  //      |       BLStub-Descriptor
+  //      |       BLStub-ReturnAddr
+  //      |       BLStub-StubPointer          |
+  //      +------ BLStub-SavedFramePointer    |- Descriptor.Size
+  //              ... arguments ...           |
+  //              ActualArgc          |
+  //              CalleeToken         |- JitFrameLayout::Size()
+  //              Descriptor          |
+  //    FP -----> ReturnAddr          |
+  //
+  // We take advantage of the fact that the stub frame saves the frame
+  // pointer pointing to the baseline frame, so a bunch of calculation can
+  // be avoided.
+  //
+  masm.bind(&handle_BaselineStub);
+  {
+    BaseIndex stubFrameReturnAddr(
+        StackPointer, scratch1, TimesOne,
+        JitFrameLayout::Size() +
+            BaselineStubFrameLayout::offsetOfReturnAddress());
+    masm.loadPtr(stubFrameReturnAddr, scratch2);
+    masm.storePtr(scratch2, lastProfilingCallSite);
+
+    BaseIndex stubFrameSavedFramePtr(
+        StackPointer, scratch1, TimesOne,
+        JitFrameLayout::Size() - (2 * sizeof(void*)));
+    masm.loadPtr(stubFrameSavedFramePtr, scratch2);
+    masm.addPtr(Imm32(sizeof(void*)), scratch2);  // Skip past BL-PrevFramePtr
+    masm.storePtr(scratch2, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::Rectifier
+  //
+  // The rectifier frame can be preceded by either an IonJS, a BaselineStub,
+  // or a CppToJSJit/WasmToJSJit frame.
+  //
+  // Stack layout if caller of rectifier was Ion or CppToJSJit/WasmToJSJit:
+  //
+  //              Ion-Descriptor
+  //              Ion-ReturnAddr
+  //              ... ion frame data ... |- Rect-Descriptor.Size
+  //              < COMMON LAYOUT >
+  //
+  // Stack layout if caller of rectifier was Baseline:
+  //
+  //              BL-Descriptor
+  // Prev-FP ---> BL-ReturnAddr
+  //      +-----> BL-SavedFramePointer
+  //      |       ... baseline frame data ...
+  //      |       BLStub-Descriptor
+  //      |       BLStub-ReturnAddr
+  //      |       BLStub-StubPointer          |
+  //      +------ BLStub-SavedFramePointer    |- Rect-Descriptor.Size
+  //              ... args to rectifier ...   |
+  //              < COMMON LAYOUT >
+  //
+  // Common stack layout:
+  //
+  //              ActualArgc          |
+  //              CalleeToken         |- IonRectitiferFrameLayout::Size()
+  //              Rect-Descriptor     |
+  //              Rect-ReturnAddr     |
+  //              ... rectifier data & args ... |- Descriptor.Size
+  //              ActualArgc      |
+  //              CalleeToken     |- JitFrameLayout::Size()
+  //              Descriptor      |
+  //    FP -----> ReturnAddr      |
+  //
+  masm.bind(&handle_Rectifier);
+  {
+    // scratch2 := StackPointer + Descriptor.size + JitFrameLayout::Size()
+    masm.lea(Operand(StackPointer, scratch1, TimesOne, JitFrameLayout::Size()),
+             scratch2);
+    masm.loadPtr(Address(scratch2, RectifierFrameLayout::offsetOfDescriptor()),
+                 scratch3);
+    masm.movePtr(scratch3, scratch1);
+    masm.and32(Imm32((1 << FRAMETYPE_BITS) - 1), scratch3);
+    masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch1);
+
+    // Now |scratch1| contains Rect-Descriptor.Size
+    // and |scratch2| points to Rectifier frame
+    // and |scratch3| contains Rect-Descriptor.Type
+
+    masm.assertRectifierFrameParentType(scratch3);
+
+    // Check for either Ion or BaselineStub frame.
+    Label notIonFrame;
+    masm.branch32(Assembler::NotEqual, scratch3, Imm32(FrameType::IonJS),
+                  &notIonFrame);
+
+    // Handle Rectifier <- IonJS
+    // scratch3 := RectFrame[ReturnAddr]
+    masm.loadPtr(
+        Address(scratch2, RectifierFrameLayout::offsetOfReturnAddress()),
+        scratch3);
+    masm.storePtr(scratch3, lastProfilingCallSite);
+
+    // scratch3 := RectFrame + Rect-Descriptor.Size +
+    //             RectifierFrameLayout::Size()
+    masm.lea(
+        Operand(scratch2, scratch1, TimesOne, RectifierFrameLayout::Size()),
+        scratch3);
+    masm.storePtr(scratch3, lastProfilingFrame);
+    masm.ret();
+
+    masm.bind(&notIonFrame);
+
+    // Check for either BaselineStub or a CppToJSJit/WasmToJSJit entry
+    // frame.
+    masm.branch32(Assembler::NotEqual, scratch3, Imm32(FrameType::BaselineStub),
+                  &handle_Entry);
+
+    // Handle Rectifier <- BaselineStub <- BaselineJS
+    BaseIndex stubFrameReturnAddr(
+        scratch2, scratch1, TimesOne,
+        RectifierFrameLayout::Size() +
+            BaselineStubFrameLayout::offsetOfReturnAddress());
+    masm.loadPtr(stubFrameReturnAddr, scratch3);
+    masm.storePtr(scratch3, lastProfilingCallSite);
+
+    BaseIndex stubFrameSavedFramePtr(
+        scratch2, scratch1, TimesOne,
+        RectifierFrameLayout::Size() - (2 * sizeof(void*)));
+    masm.loadPtr(stubFrameSavedFramePtr, scratch3);
+    masm.addPtr(Imm32(sizeof(void*)), scratch3);
+    masm.storePtr(scratch3, lastProfilingFrame);
+    masm.ret();
+  }
+
+  // FrameType::IonICCall
+  //
+  // The caller is always an IonJS frame.
+  //
+  //              Ion-Descriptor
+  //              Ion-ReturnAddr
+  //              ... ion frame data ... |- CallFrame-Descriptor.Size
+  //              StubCode               |
+  //              ICCallFrame-Descriptor |- IonICCallFrameLayout::Size()
+  //              ICCallFrame-ReturnAddr |
+  //              ... call frame data & args ... |- Descriptor.Size
+  //              ActualArgc      |
+  //              CalleeToken     |- JitFrameLayout::Size()
+  //              Descriptor      |
+  //    FP -----> ReturnAddr      |
+  masm.bind(&handle_IonICCall);
+  {
+    // scratch2 := StackPointer + Descriptor.size + JitFrameLayout::Size()
+    masm.lea(Operand(StackPointer, scratch1, TimesOne, JitFrameLayout::Size()),
+             scratch2);
+
+    // scratch3 := ICCallFrame-Descriptor.Size
+    masm.loadPtr(Address(scratch2, IonICCallFrameLayout::offsetOfDescriptor()),
+                 scratch3);
+#ifdef DEBUG
+    // Assert previous frame is an IonJS frame.
+    masm.movePtr(scratch3, scratch1);
+    masm.and32(Imm32((1 << FRAMETYPE_BITS) - 1), scratch1);
+    {
+      Label checkOk;
+      masm.branch32(Assembler::Equal, scratch1, Imm32(FrameType::IonJS),
+                    &checkOk);
+      masm.assumeUnreachable("IonICCall frame must be preceded by IonJS frame");
+      masm.bind(&checkOk);
+    }
+#endif
+    masm.rshiftPtr(Imm32(FRAMESIZE_SHIFT), scratch3);
+
+    // lastProfilingCallSite := ICCallFrame-ReturnAddr
+    masm.loadPtr(
+        Address(scratch2, IonICCallFrameLayout::offsetOfReturnAddress()),
+        scratch1);
+    masm.storePtr(scratch1, lastProfilingCallSite);
+
+    // lastProfilingFrame := ICCallFrame + ICCallFrame-Descriptor.Size +
+    //                       IonICCallFrameLayout::Size()
+    masm.lea(
+        Operand(scratch2, scratch3, TimesOne, IonICCallFrameLayout::Size()),
+        scratch1);
+    masm.storePtr(scratch1, lastProfilingFrame);
+    masm.ret();
+  }
+
+  //
+  // FrameType::CppToJSJit / FrameType::WasmToJSJit
+  //
+  // If at an entry frame, store null into both fields.
+  // A fast-path wasm->jit transition frame is an entry frame from the point
+  // of view of the JIT.
+  //
+  masm.bind(&handle_Entry);
+  {
+    masm.movePtr(ImmPtr(nullptr), scratch1);
+    masm.storePtr(scratch1, lastProfilingCallSite);
+    masm.storePtr(scratch1, lastProfilingFrame);
+    masm.ret();
+  }
+}